I just did the extraction and it looks fine on my computer. Does the extraction look OK on your computer before you run it through SPA?
Here is a screenshot of the image extracted on my computer. I put yellow in the background to make it easy to see if there was any white left over, which there is not.
I can’t see any way that EZ Green Screen could add white spots in areas that were green. It looks to me like the image was extracted, then flattened on white, and then the white was extracted with Select Subject or the Image Extract plugin. Did you only use EZ Green Screen? Or did you also use Image Extract?
If the extraction itself look OK but you only see the white when running SPA, are you using any custom Photoshop action sin your SPA process?